1. Field of the Invention
The present invention relates to a safety system for a liquid fuel tank.
2. Discussion of Background
Many safety systems relating to fuel tanks have been described and pertain in general to solving the problems associated with degassing of the tank, while it is being filled, and venting it during normal periods when the engine is at rest and when it is in operation and consuming this fuel. Added to these problems is the increasingly urgent need, as regards protecting the environment, to recover the vapours released during the abovementioned operations, by as far as possible preventing any leakage into the atmosphere.
U.S. Pat. No. 5,183,087 teaches how to degas a fuel tank provided with a fill tube, with a degassing and venting valve connected to a canister and with a small-diameter pipe connecting the upper part of the tank to a guide located at the inlet of the fill tube, the function of which is to initiate the closure of the fuel supply via the nozzle. This guide is provided with a sealing device and the pipe terminates downstream of the sealing device. In this system, degassing takes place exclusively via the valve connected to the canister. This valve is normally closed in the rest position and opens only under the effect of a certain pressure in the tank.
However, the known systems have a number of drawbacks:                difficult control of the overpressure in the tank bringing about inopportune spillages and splashing when filling;        system ill-suited to recovering the vapours via the nozzle;        impossibility of closing off the fuel supply via the nozzle for an overfilling of less than 0.2 l.        